1. Field of the Invention
This invention relates to an electrical safety circuit for driving an electrically driven vehicle such as a dump truck. More particularly, this invention relates to a circuit for use in dump trucks of the type used in strip mining operations. Such dump trucks are extremely large (over 100 ton payload capacity) and therefore potentially dangerous, and the inclusion of safety features is thus very important.
2. Description of the Prior Art
A conventional electrical circuit for driving such a vehicle is not coupled in a sequence or interlock circuit relation to other electrical circuits of the vehicle such as brake and dump controls which are provided separately from the driving circuit. This causes various problems, including the following ones:
(a) The vehicle starts moving if an operator erroneously depresses an accelerator pedal without releasing a parking brake with the result being that a parking brake drum is burnt. PA1 (b) If a driver of a dump car working in a dumping place erroneously depresses the accelerator pedal while operating a dump control lever without having shifted a forward-reverse movement change lever from a reverse position to a neutral position, the dump truck moves in reverse, which gives rise to the danger that the truck will fall into the dump pit.
It is, therefore, an object of the present invention to provide an electrical circuit for driving a dump truck which eliminates the above described problems inherent in conventional electrical driving circuits.
It is another object of the invention to provide an electrical circuit for driving an electrically driven dump truck capable of preventing an erroneous starting of the vehicle by maintaining a control circuit in the electrical driving circuit disconnected from its power source unless the operator operates the vehicle correctly.
It is yet another object of the invention to provide a dump truck which includes a safety control circuit in combination with a dynamic braking system, thereby maximizing the safety of the dump truck.